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Alternative names Return to top
Cold agglutinins; Weil-Felix reaction; Widal's testDefinition Return to top
This test measures the level of warm or cold agglutinins in blood. Agglutinins are antibodies that cause the red blood cells to gather together. Cold agglutinins are active at cold temperatures. Warm agglutinins are active at normal body temperature.How the test is performed Return to top
Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and an elastic band or blood pressure cuff is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the band to swell.
A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the band is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.
In infants or young children, the area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. Cotton or a bandage may be applied to the puncture site if there is any continued bleeding.
The sample is collected in a tube that has been warmed to normal body temperature (98.6 degrees F) and sent to a laboratory.
How to prepare for the test Return to top
There is no special preparation.How the test will feel Return to top
When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.Why the test is performed Return to top
These antibodies can cause a hemolytic anemia. This occurs when the body destroys its own red blood cells. Distinguishing between warm and cold agglutinins can help understand why the hemolytic anemia is occuring and directs therapy.Normal Values Return to top
What abnormal results mean Return to top
Elevated levels of cold or warm agglutinins can cause hemolytic anemia. Some patients with moderately elevated levels will have no hemolysis and likely won't require therapy.
The presence of warm agglutinins may occur with:
What the risks are Return to top
Special considerations Return to top
If cold agglutinin disease is suspected, the individual needs to be kept warm. Update Date: 9/11/2003 Updated by: Megan E. B. Clowse, M.D., M.P.H., Division of Rheumatology, Johns Hopkins Hospital, Baltimore, MD. Review provided by VeriMed Healthcare Network.
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Page last updated: 28 October 2004 |